Passive Liquid Cooling System for Inverters Utilized for Wind Turbine Applications

ABSTRACT

A wind turbine with a thermal siphoning system is disclosed. The wind turbine comprises a tower of a wind turbine, the tower having a top and a base, and a thermal siphoning system for cooling heat generating components. The thermal siphoning system is located within the wind turbine tower and comprises a liquid coolant and at least one heat generating component located near the base of the tower. The heat generating component is adapted to receive the coolant through a coolant inlet port and adapted to discharge the coolant through a coolant outlet port. The thermal siphoning system further comprises a hot coolant tube connected to the coolant outlet port of the heat generating component.

TECHNICAL FIELD

The present disclosure relates generally to wind turbines and, more particularly, to a passive liquid cooling system for inverters within a wind turbine.

BACKGROUND

In recent years, wind turbines have been integrated into electric power generation systems to create electricity to support the needs of both industrial and residential applications. These wind turbines capture the kinetic energy of the wind and convert it into electricity. A typical wind turbine includes a set of two or three large blades mounted to a hub. Together, the blades and hub are referred to as the rotor. The rotor is connected to a main shaft, which in turn, is connected to a generator. When the wind causes the rotor to rotate, the kinetic energy of the wind is captured and converted into rotational energy. The rotational energy of the rotor is translated along the main shaft to the generator, which then converts the rotational energy into electricity. The electricity produced by the wind turbine is then distributed to a power utility grid for industrial and residential use.

As of late, wind turbine designers have begun to increase the power output of a wind turbine system by increasing the efficiency of the electric power generation system. This has been accomplished by utilizing permanent magnet generators, which have a much higher efficiency than induction or wound field generators. Permanent magnet generators create alternating current, or AC electric power. The frequency of the AC waveform is directly proportional to the rotational speed of the generator. Since the utility grid operates at a fixed 60 Hz frequency, the variable alternating frequency of the permanent magnet generator must be conditioned to a fixed 60 Hz frequency. Typically, this is accomplished by rectifying the variable alternating current (AC) frequency of the permanent magnet generator into a fixed direct current (DC) power via a passive or active rectifier. This DC power is then sent to an inverter that produces a constant frequency of 60 Hz in AC power output.

Historically, the inverters utilized to produce a constant frequency AC power output have been large air cooled devices. In an effort to reduce the size and cost of the inverters, while increasing their reliability, wind turbine designers have begun to explore the use of liquid cooled inverters. Liquid cooled inverters are smaller, cheaper, and more reliable than their air cooled counterparts. However, the drawback to the liquid cooled inverter is the need to provide the inverter with pressurized thermally conditioned coolant. Typically, these pressurized thermal cooling systems for the liquid cooled inverter can be very expensive. In addition, there are many parts associated with a conventional liquid coolant conditioning system, such as the pump assembly which includes a pump with dynamic seals, an electric motor, and the motor's control system, the air to water heat exchanger, and the air blower that forces air through the air to water heat exchanger. These parts not only raise the capital costs required to build the wind turbine system as a whole, but also increase maintenance costs associated with the liquid cooled inverter.

Thus, there exists a need for a simplified, inexpensive and reliable liquid coolant conditioning system. This disclosure is directed to solving this need and provides a way to reduce the cost and complexity of the liquid coolant conditioning system for a liquid cooled inverter of a wind turbine.

SUMMARY OF THE INVENTION

According to one embodiment of the present disclosure, a wind turbine is disclosed. The wind turbine may comprise a tower of a wind turbine, the tower having a top and a base, and a thermal siphoning system for cooling heat generating components. The thermal siphoning system may be located within the wind turbine tower and may comprise a liquid coolant and at least one heat generating component located near the base of the tower. The heat generating component may be adapted to receive the coolant through a coolant inlet port and may be adapted to discharge the coolant through a coolant outlet port. The thermal siphoning system may further comprise a hot coolant tube connected to the coolant outlet port of the heat generating component. The hot tube may be mounted in direct thermal contact with the inner surface of the tower and may extend up from near the base of the tower to near the top of the tower. The thermal siphoning system may further comprise a return coolant tube connected to the hot tube at the top of the tower and extending down to near the base of the tower. The return tube may be parallel to the hot tube and connected to the coolant inlet port of the heat generating component.

According to another embodiment, a thermal siphoning system for cooling heat generating components in a wind turbine is disclosed. The thermal siphoning system may comprise a liquid coolant and at least one heat generating component located near a base of a tower of a wind turbine, the heat generating component adapted to receive the coolant through a coolant inlet port and adapted to discharge the coolant through a coolant outlet port. The thermal siphoning system may further comprise a hot coolant tube connected to the coolant outlet port of the heat generating component, the hot tube mounted in direct thermal contact with the inner surface of the tower and extending up from near the base of the tower to near a top of the tower, and a return coolant tube connected to the hot tube at the top of the tower and extending down to near the base of the tower, the return tube parallel to the hot tube and connected to the coolant inlet port of the heat generating component.

According to yet another embodiment, a method for cooling heat generating components in a wind turbine is disclosed. The method may comprise providing a wind turbine with a tower having a top and a base, and a thermal siphoning system located within the tower. The thermal siphoning system may comprise a liquid coolant, at least one heat generating component located near the base of the tower, the heat generating component having a coolant inlet port and a coolant outlet port, a hot coolant tube connected to the coolant outlet port of the heat generating component and mounted in direct thermal contact with the inner surface of the tower, the hot coolant tube extending up to near the top of the tower, and a return coolant tube connected between the hot tube at the top of the tower and the coolant inlet port of the heat generating component near the base of the tower. The method may further comprise transferring the heat generated by the heat generating component to the liquid coolant, discharging the liquid coolant out of the heat generating component through the coolant outlet port and into the hot tube, transferring the heat from the coolant within the hot tube to the inner surface of the tower as the coolant rises up the hot tube to near the top of the tower, and dissipating the heat from the inner surface of the tower to the atmosphere.

These and other aspects and features of the disclosure will become more readily apparent upon reading the following detailed description when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a wind turbine made according to one embodiment of the present disclosure;

FIG. 2 is a partial cutaway view of the wind turbine tower of FIG. 1;

FIG. 3 is a partial cutaway view of a wind turbine tower according to another embodiment of the present disclosure; and

FIG. 4 is an exemplary flowchart outlining the flow of liquid coolant through the components of the thermal siphoning system of FIG. 3.

DETAILED DESCRIPTION

While the following detailed description has been given and will be provided with respect to certain specific embodiments, it is to be understood that the scope of the disclosure should not be limited to such embodiments, but that the same are provided simply for enablement and best mode purposes. The breadth and spirit of the present disclosure is broader than the embodiments specifically disclosed and encompassed with the claims appended hereto.

Referring to FIGS. 1 and 2, a wind turbine 10 according to one embodiment of the present disclosure is shown. While all components of the wind turbine 10 are not shown or described herein, the wind turbine 10 may include a vertically oriented tower 12. Typically, the tower 12 of a wind turbine 10 may extend, for example, upwards to a height of, including but not limited to, two hundred and forty vertical feet (240 ft.) at which the wind turbine 10 can optimally capture the kinetic energy of the wind. The tower 12 may have a top 14, a base 16, and a tower wall 18. The tower wall 18 may define a generally enclosed space inside the tower 10 from the atmosphere A. The tower wall 18 may have an inner surface 20 and an outer surface 22 and may be composed of stainless steel, steel, concrete, or any other material suited for wind turbine tower construction. Other heights and materials are certainly possible.

A nacelle 30 may be rotatably mounted at the top 14 of the tower 12 with a hub 32 mounted for rotation to the nacelle 30. Radially extending from the hub 32 are a plurality of blades 34. Together, the hub 32 and blades 34 are referred to as the rotor 36. The rotor 36 may be mounted to a main shaft 38 within the nacelle 30. The main shaft 38 is operatively connected to a generator 40, which may also be contained within the nacelle 30. The generator 40 may be operatively connected (via electrical conductors 42) to one or more heat generating components 44 located at the base 16 of the tower 12. The heat generating components 44 condition the electric power from the generator 40 for distribution to the utility power grid (not shown). Non-limiting examples of heat generating components 44 may include any electric power conversion or conditioning system, generator control system, passive rectifier, active rectifier, transformer, inverter, and/or liquid cooled inverter.

As shown best in FIG. 2, the tower 12 of the wind turbine 10 may contain a thermal siphoning system 60 for cooling the heat generating components 44. The thermal siphoning system 60 may comprise a liquid coolant 62, the at least one heat generating component 44, a hot coolant tube 64, and a return coolant tube 66. Mounted at the base 16 of the tower 12, the heat generating component 44 may be adapted to receive the liquid coolant 62 through a coolant inlet port 70 and be adapted to discharge the liquid coolant 62 through a coolant outlet port 72. The hot coolant tube 64 is connected via a coolant outlet tube 74 to the coolant outlet port 72 of the heat generating component 44 at the base 16 of the tower 12. Vertically oriented, the hot tube 64 is mounted in direct thermal contact to the inner surface 20 of the tower wall 18 and extends up from near the tower base 16 to near the top 14 of the tower 12. The hot tube 64 may run along the inner surface 20 of the tower wall 18 for the entire height of the tower 12. The hot tube 64 may be bolted to the tower wall 18 on one side 80 of the tower 12 by way of support structures 82. Other acceptable methods for thermally attaching the hot tube 64 to the tower wall 18 include but are not limited to welding, brazing, or thermal bonding.

Connected to the hot tube 64 at the top 14 of the tower 12 via a connecting tube 78, the return coolant tube 66 runs parallel to the hot tube 64 and extends down to near the base 16 of the tower 12. The return coolant tube 66 may also be mounted in direct thermal contact to the inner surface 20 of the tower wall 18 for the entire height of the tower 12. By way of support structures 82, the return tube 66 may be bolted to the tower wall 18 on the opposite side 84 of the tower 12. Other acceptable methods for thermally attaching the hot tube 66 to the tower wall 18 include but are not limited to welding, brazing, or thermal bonding. At the base 16 of the tower 12, the return coolant tube 66 is connected to the coolant inlet port 70 of the heat generating component 44 via a coolant inlet tube 76. Although shown and described as being mounted to the inner surface 20 of the tower wall 18 in FIG. 2, the return tube 66 may not be mounted in direct thermal contact to the inner surface 20 of the tower wall 18 and also may not be mounted to the opposite side 84 of the tower 12. In addition, although shown and described as being mounted to the inner surface 20 of the tower wall 18 in FIG. 2, the hot tube 64 and/or return tube 66 may be mounted to an outer surface of the tower wall 18 without departing from the scope of the disclosure.

Furthermore, although referred to as having separate tubes (hot coolant tube 64, return coolant tube 66, coolant outlet tube 74, coolant inlet tube 76, and connecting tube 78), the thermal siphoning system 60 may comprise one continuous tube connected to the coolant inlet and outlet ports 70, 72 of the heat generating component 44, or any number and combination of tubes thereof, as long as a siphon effect is created within the tower 12. In addition, although described as having only one hot coolant tube 64, one return coolant tube 66, one coolant outlet tube 74, one coolant inlet tube 76, and one connecting tube 78, the thermal siphoning system 60 may comprise more than one hot tube 64, more than one coolant tube 66, more than one outlet tube 74, more than one inlet tube 76, and/or more than one connecting tube 78 and any combination of number of tubes without departing from the scope of the present disclosure. For example, the thermal siphoning system 60 may comprise two or more hot tubes 64 running parallel to two or more return tubes 66, two or more hot tubes 64 running parallel to one return tube 66, one hot tube 64 running parallel to two or more return tubes, or any other desired combination thereof. Non-limiting examples of tubing material include copper, aluminum, iron, steel, stainless steel, galvanized pipe (i.e. steel pipe coated with zinc), black pipe (i.e. steel pipe coated with black oxide), bronze, brass, and plastic. Although these named tubing materials make for good thermal conductors, any thermal conducting material may be used for the thermal siphoning tubes. Non-limiting examples of liquid coolant 62 include water, ethylene glycol, diethylene glycol, propylene glycol, or any mixture or combination thereof.

As the heat generating component 44 within the tower 12 generates heat, the heat is transferred to the liquid coolant 62. The liquid coolant 62 is then discharged out of the heat generating component 44 through the coolant outlet port 72 and into the coolant outlet tube 74 and hot tube 64. As the temperature of the coolant 62 rises due to the heat absorbed from the heat generating component 44, the density of the coolant 62 decreases, which in turn, results in the heated coolant 62 rising up the hot tube 64. As the coolant 62 travels up the height of the tower 12 in the hot tube 64 to near the top 14 of the tower 12, the heat is transferred from the coolant 62 in the hot tube 64 to the inner surface 20 of the tower wall 18. The heat is then conducted through the tower wall 18 to the outer surface 22 of the tower wall 18, where it is dissipated into the atmosphere A. Due to the winds blowing over the outer surface 22 of the tower wall 18, the thermal path from the hot tube 64 to the outer surface 22 of the tower wall 18 provides for the optimal removal of heat from the coolant 62 and into the atmosphere A.

As the heat is transferred to the tower wall 18, the liquid coolant 62 in the hot coolant tube 64 loses heat. By the time the coolant 62 reaches the top 14 of the tower in the hot and connecting tubes 64, 78, the temperature of the coolant 62 will be near ambient temperature. Since the heat in the coolant 62 at the top 14 of the tower 12 has been dissipated into the atmosphere, the density of the coolant 62 at the top 14 of the tower 12 will be higher than that of the warmer coolant 62 trying to travel up the hot tube 64. As a result, the coolant 62 at the top 14 of the tower 12 will flow down the return coolant tube 66. The return tube 66 facilitates the flow of the coolant 62 down the height of the tower 12 into the coolant inlet tube 76 and back into the heat generating component 44 through the coolant inlet port 70. Due to the thermal path from the return tube 66 to the outer surface 22 of the tower wall 18, more heat dissipation may occur from the coolant 62 to the atmosphere A. Therefore, the temperature of the coolant 62 which is recycled back into the heat generating component 44 will be lower because the heat is removed from the coolant 62 via the thermal paths of the hot and return tubes 64, 66 to the tower wall 18. In this way, the thermal siphoning system 60 delivers thermally conditioned coolant 62 to the heat generating component 44.

As the colder, thermally conditioned coolant 62 is recycled through the heat generating component 44, it will once again absorb heat from the heat generating component 44 and the process will repeat itself. By utilizing the change in density of the liquid coolant 62 in concert with the physical characteristics of the wind turbine tower 12, such as the height of the tower 10, the thermal siphoning system 60 creates a siphon effect through the hot and return coolant tubes 64, 66. The siphon effect provides the motive power to force the coolant 62 through the heat generating component 44. This results in a continuously flowing channel of liquid coolant 62, and therefore, a passive liquid cooling system for the heat generating component 44. By eliminating the need for many components included in a conventional liquid coolant conditioning system, i.e., the pump assembly (along with the parts of the pump assembly, such as the pump, dynamic seals, electric motor, and motor control system), the air to water heat exchanger, and air blower that forces air through the air to water heat exchanger, the thermal siphoning system of the present disclosure significantly reduces the cost of the liquid coolant conditioning system, while radically increasing its reliability. In addition, the capital costs required to build the wind turbine system and the maintenance costs associated with the cooling system are also reduced through the simplicity and efficiency of the thermal siphoning system of the present disclosure.

Although not shown in FIGS. 1 and 2, the thermal siphoning system may also include one or more filters, reservoirs, passive or active thermal control valves, thermostats, and/or localized bypass loops. Filters may be used within the tubes of the thermal siphoning system to keep the working fluid relatively clean by filtering out debris caused by corrosion of the tubes. Reservoirs may be used to contain a reserve amount of hot or cold coolant for the thermal siphoning system. A thermal control valve or thermostat may be utilized to control the temperature of the coolant entering the heat generating component. A localized bypass loop may be utilized to connect the return tube to the hot tube.

According to another embodiment shown in FIG. 3, a thermal siphoning system 160 of a wind turbine tower 112 is disclosed. The thermal siphoning system 160 may include a localized bypass loop 102 and a thermal control valve 100. The localized bypass loop 102 connects the return coolant tube 166 to the hot coolant tube 164 at the base 116 of the tower 112 and provides for a direct path for the coolant 162 to flow from the return tube 166 to the hot tube 164 while bypassing the heat generating component 144. Connected to the return tube 166, localized bypass loop 102, and coolant inlet port 172 of the heat generating component 144, the thermal control valve 100 may control the temperature of the coolant 162 entering the heat generating component 144 and may be comprised of a T valve. A T valve is a type of valve in the shape of a “T” that connects three tubes together and controls the flow of liquid into and out of the tubes.

Depending on the temperature of the liquid coolant 162, the thermal control valve 100 may either allow the coolant 162 from the return tube 166 to enter the heat generating component 144 or restrict the coolant 162 from the return tube 166 from entering the heat generating component 144. If the coolant 162 from the return tube 166 is restricted from entering the heat generating component 144 by the thermal control valve 100, the coolant 162 will then flow through the localized bypass loop 102 and bypass the heat generating component 144. Although not shown, another localized bypass loop and/or a reservoir may be used in addition to the thermal control valve 100 and the localized bypass loop 102 in order to supply hot or cold coolant to be mixed in with the coolant from the return tube 166. In this way, the thermal control valve 100 can ensure the temperature of coolant 162 entering the heat generating component 144.

Referring now to FIG. 4, an exemplary flowchart 180 outlining the flow of the liquid coolant 162 through the components of the thermal siphoning system 160 of FIG. 3 is shown. After starting at a step 182, the liquid coolant 162 flows through the heat generating component 144, where the heat is transferred from the heat generating component 144 and into the coolant 162. The coolant 162 flows out of the heat generating component 144 and into the hot coolant tube 164, where the heat is transferred from the hot coolant tube 164 to the tower wall and dissipated into the atmosphere. From the hot tube 164 at the top of the tower, the coolant 162 flows into the return coolant tube 166. From the return coolant tube 166, the coolant 162 flows into the thermal control valve 100. The thermal control valve 100 then determines whether the coolant 162 from the return tube 166 is at the desired temperature, or within a desired temperature range. If the coolant 162 is at the desired temperature, then the coolant 162 is sent through to the heat generating component 144, where the process starts over again and the liquid coolant 162 absorbs more heat from the heat generating component 144. If the coolant 162 is not at the desired temperature, then the coolant 162 is sent to the localized bypass loop 102. When sent to the bypass loop 102, the coolant 162 bypasses the heat generating component 144 and flows directly into the hot tube 164, where the process is continued and restarted therefrom. As shown in the flowchart 180, a continuously flowing channel of temperature-controlled liquid coolant 162 is utilized to passively cool the heat generating component 144.

In another embodiment of the present disclosure shown in FIG. 5, a thermal siphoning system 260 may comprise at least one heat generating component 244, an air to water heat exchanger 290, and a liquid coolant (not shown). The heat generating component 244 may be mounted within the nacelle 230. The air to water heat exchanger 290 may be operatively connected to the heat generating component 244. The air to water heat exchanger 290 may be mounted outside of the wind turbine 210 at a height differential Δ above the nacelle 230 in the windstream of the atmosphere A. The liquid coolant may run throughout the heat generating component 244 and the air to water heat exchanger 290. The liquid coolant transfers the heat from the heat generating component 244 to the air to water heat exchanger 290. Air from the atmosphere A will passively blow through the air to water heat exchanger 290 to provide cooling to the liquid coolant. Once cooled, the liquid coolant will return from the air to water heat exchanger 290 to the heat generating component 244, where the process repeats itself. The height differential Δ between the air to water heat exchanger 290 above the nacelle 230 and the heat generating component 244 inside the nacelle 230 will induce a siphoning effect and drive the liquid coolant through the thermal siphoning system 260 to remove heat from and cool the heat generating component 244.

From the foregoing, it can be seen that the present disclosure sets forth improved cooling systems which can be used to keep operating components of a wind turbine at a desired temperature. Moreover, by being passive in design, the cooling system not only keeps the components of the wind turbine, particularly the electrical components of the wind turbine, at a desired temperature, but also does so in an energy efficient manner to thus keep operating costs as well as initial construction costs low. 

What is claimed is:
 1. A wind turbine comprising: a tower of a wind turbine, the tower having a top and a base; and a thermal siphoning system for cooling heat generating components, the thermal siphoning system located within the wind turbine tower and comprising: a liquid coolant; at least one heat generating component located near the base of the tower, the heat generating component adapted to receive the coolant through a coolant inlet port and adapted to discharge the coolant through a coolant outlet port; a hot coolant tube connected to the coolant outlet port of the heat generating component, the hot tube mounted in direct thermal contact with the inner surface of the tower and extending up from near the base of the tower to near the top of the tower; and a return coolant tube connected to the hot tube at the top of the tower and extending down to near the base of the tower, the return tube parallel to the hot tube and connected to the coolant inlet port of the heat generating component.
 2. The wind turbine of claim 1, wherein, the thermal siphoning system further comprises at least one filter.
 3. The wind turbine of claim 1, wherein the thermal siphoning system further comprises at least one reservoir.
 4. The wind turbine of claim 1, wherein the thermal siphoning system further comprises a thermal control valve.
 5. The wind turbine of claim 1, wherein the thermal siphoning system further comprises a bypass loop which connects the return tube to the hot tube near the base of the tower.
 6. The wind turbine of claim 1, wherein the heat generating component comprises a liquid cooled inverter.
 7. The wind turbine of claim 1, wherein the return coolant tube is mounted in direct thermal contact with the inner surface of the tower.
 8. The wind turbine of claim 7, wherein a third tube connects the hot coolant tube to the return coolant tube, the third tube perpendicularly oriented to the hot and return tubes and located near the top of the tower.
 9. The wind turbine of claim 1, wherein the thermal siphoning system utilizes the liquid coolant's change in density and the height of the tower to create a siphon effect through the hot and return coolant tubes.
 10. The wind turbine of claim 1, wherein the heat generated by the heat generating component is transferred to the liquid coolant, which is discharged from the coolant outlet port of the heat generating component and into the hot tube, where the heat is transferred from the coolant to the inner surface of the tower as the coolant rises up the hot tube to near the top of the tower.
 11. The wind turbine of claim 10, wherein heat transferred from the coolant to the inner surface of the tower is dissipated to the atmosphere.
 12. The wind turbine of claim 11, wherein the coolant in the hot tube near the top of the tower flows down the return tube and back into the heat generating component through the coolant inlet port.
 13. A thermal siphoning system for cooling heat generating components in a wind turbine comprising: a liquid coolant; at least one heat generating component located near a base of a tower of a wind turbine, the heat generating component adapted to receive the coolant through a coolant inlet port and adapted to discharge the coolant through a coolant outlet port; a hot coolant tube connected to the coolant outlet port of the heat generating component, the hot tube mounted in direct thermal contact with the inner surface of the tower and extending up from near the base of the tower to near a top of the tower; and a return coolant tube connected to the hot tube at the top of the tower and extending down to near the base of the tower, the return tube parallel to the hot tube and connected to the coolant inlet port of the heat generating component.
 14. The thermal siphoning system of claim 13, wherein a siphon effect is created through the hot and return coolant tubes by utilizing the liquid coolant's change in density and the height of the tower.
 15. The thermal siphoning system of claim 14, wherein the heat generated by the heat generating component is transferred to the liquid coolant, which is discharged from the coolant outlet port of the heat generating component and into the hot tube, where the heat is transferred from the coolant to the inner surface of the tower as the coolant rises up the hot tube to near the top of the tower.
 16. The thermal siphoning system of claim 15, wherein heat transferred from the coolant to the inner surface of the tower is dissipated to the atmosphere.
 17. The thermal siphoning system of claim 16, wherein the coolant in the hot tube near the top of the tower flows down the return tube and back into the heat generating component through the coolant inlet port.
 18. A method for cooling heat generating components in a wind turbine comprising: providing a wind turbine with a tower having a top and a base, and a thermal siphoning system located within the tower, the thermal siphoning system comprising a liquid coolant, at least one heat generating component located near the base of the tower, the heat generating component having a coolant inlet port and a coolant outlet port, a hot coolant tube connected to the coolant outlet port of the heat generating component and mounted in direct thermal contact with the inner surface of the tower, the hot coolant tube extending up to near the top of the tower, and a return coolant tube connected between the hot tube at the top of the tower and the coolant inlet port of the heat generating component near the base of the tower; transferring the heat generated by the heat generating component to the liquid coolant; discharging the liquid coolant out of the heat generating component through the coolant outlet port and into the hot tube; transferring the heat from the coolant within the hot tube to the inner surface of the tower as the coolant rises up the hot tube to near the top of the tower; and dissipating the heat from the inner surface of the tower to the atmosphere.
 19. The method of claim 18, further comprising utilizing the liquid coolant's change in density and the tower's height to create a siphon effect through the hot and return coolant tubes.
 20. A thermal siphoning system for cooling heat generating components in a wind turbine comprising: at least one heat generating component located within a nacelle of a wind turbine; an air to water heat exchanger operatively connected to the heat generating component, the air to water heat exchanger located outside of the wind turbine at a height above the nacelle of the wind turbine; and a liquid coolant running throughout the heat generating component and the air to water heat exchanger. 